Aerosol containers of the barrier pack type include the well-known piston-in-can, and bag-in-can, embodiments. In one form of the latter, to which the present invention is directed, a flexible bag within the can may have its open end sealingly connected to the valve housing of the aerosol valve. Such embodiments are referred to as bag-on-valve systems. The product to be dispensed from the aerosol container commonly is filled into the flexible bag within the container and a liquified propellant or compressed gas is filled into the aerosol container outside of the bag between the bag outer wall and the inner wall of the can. When the aerosol valve is actuated, the propellant acts against the outer wall of the bag to force the product being dispensed out the aerosol valve to the environment outside the can. When the valve actuation cases, of course, the product dispensing ceases.
Heretofore, the filling of the propellant into the container outside of the bag usually has been accomplished by filling propellant under the mounting cup or through the bottom of the container or by other complex schemes and structure. Such forms of propellant filling may require special and expensive filling equipment not owned by many commercial fillers who generally do own conventional pressure filling equipment to fill aerosol containers that do not include bag-on-valve systems. Such prior art forms of propellant filling can also be slow. In addition, prior art bag-on-valve systems do not generally permit product and propellant pressure filling to separately occur after the valve has been fixed to the container, such that the product and propellant cannot mix and the product filling cannot be shut off by imprecise stem positioning during product filling.